000
AXPZ20 KNHC 271609
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC MON MAY 27 2013

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1500 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1200 UTC.

...SPECIAL FEATURE...

A 1008 MB LOW PRES EMBEDDED WITHIN THE MONSOON TROUGH IS LOCATED 
NEAR 13N96W...OR A COUPLE OF HUNDRED MILES SOUTH OF THE GULF OF 
TEHUANTEPEC. THE LOW IS NEARLY STATIONARY CURRENTLY...AND 
ALTHOUGH IS POORLY DEFINED AT THE SURFACE...EXHIBITED A STRONG 
BURST OF CONVECTION OVER THE PAST 12 HOURS DUE TO INTERACTIONS 
WITH THE COAST AND A SHORT WAVE TROUGH DIGGING INTO THE AREA 
FROM THE NW. THERE IS HIGH PROBABILITY OF TROPICAL CYCLONE 
FORMATION WITH THIS SYSTEM OVER THE NEXT 48 HOURS AS IT DRIFTS 
SLOWLY NW FOLLOWED BY A TURN TO THE NE. REGARDLESS OF 
DEVELOPMENT... HEAVY RAINS ARE LIKELY OVER PORTIONS OF SOUTHERN 
MEXICO AND NORTHERN CENTRAL AMERICA DURING THE NEXT FEW DAYS DUE 
TO SEVERAL DAYS OF PERSISTENTLY STRONG ONSHORE FLOW MEETING THE 
ELEVATED TERRAIN. THESE RAINS COULD PRODUCE LIFE-THREATENING 
FLASH FLOODS AND MUD SLIDES. SEE LATEST TROPICAL WEATHER OUTLOOK 
FOR MORE INFORMATION.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
MONSOON TROUGH AXIS EXTENDS FROM 11N86W TO 13N90W TO LOW PRES 
NEAR 13N96W 1008 MB TO 14N105W TO LOW PRES NEAR 11N113W 1008 MB 
TO 08N119W. ITCZ AXIS FROM 08N119W TO 09N125W TO 05N140W. 
NUMEROUS MODERATE TO ISOLATED STRONG WITHIN 120 NM S OF AXIS 
BETWEEN 85W AND 90W. NUMEROUS MODERATE SCATTERED STRONG WITHIN 
120 NM EITHER SIDE OF AXIS BETWEEN 90W AND 95W. SCATTERED 
MODERATE ISOLATED STRONG WITHIN 120 NM N OF AXIS BETWEEN 95W AND 
103W. SCATTERED MODERATE ISOLATED STRONG WITHIN 120 NM S OF AXIS 
BETWEEN 111W AND 113W. SCATTERED MODERATE WITHIN 240 NM N OF 
AXIS AND 120 S OF AXIS BETWEEN 125W AND 135W.

...DISCUSSION...

THE MAIN FORECAST ISSUE E OF 110W CONTINUES TO BE THE 
DEVELOPMENT OF THE LOW PRES AREA NEAR 13N96W. AN EARLIER SSMIS 
PASS DID NOT SHOW A CLEARLY DEFINED CENTER THIS MORNING BUT 
CONVECTION FLARED CONSIDERABLY OVERNIGHT WHERE SW FLOW 
CONVERGING INTO THE MONSOON TROUGH ENCOUNTERED NE DRAINAGE FLOW 
OFF THE MOUNTAINOUS COAST OF SOUTHERN MEXICO AND GUATEMALA. 
CONVECTION WAS FURTHER ENHANCED BY A SHORT WAVE TROUGH DIGGING 
INTO THE SW GULF OF MEXICO N OF THE AREA. 

A LINE OF CONVECTION HAS ALSO BEEN ACTIVE ALONG THE REMAINDER OF 
COAST OF CENTRAL AMERICA SOUTHWARD TO PANAMA. MOST OF THIS 
CONVECTION IS DIMINISHING EXCEPT FOR OFF THE AZUERO PENINSULA OF 
PANAMA. 

FARTHER WEST...ANOTHER LOW PRES AREA IS NOTED NEAR 11N113W 1008 
MB. THERE IS GOOD AGREEMENT AMONG THE MODELS CONCERNING THE 
POSITION AND INTENSITY OF THE IS THROUGH 24 HOURS...BUT THE GFS 
DIVERGES FROM OTHER MAJOR MODELS DEVELOPING THIS SYSTEM BY 48 
AND BEYOND AND MOVING IT NE. THE LOW PRES REMAINS IN A 
RELATIVELY UNFAVORABLE AREA OF SUBSIDENCE SE OF AN UPPER RIDGE.  
FORECAST REFLECTS CONSENSUS OF ECMWF AND UKMET BY 48 HOURS 
SHOWING MODEST DEVELOPMENT AND LITTLE MOVEMENT. 
 
ELSEWHERE...A 1028 MB HIGH PRES LOCATED NEAR 32N140W EXTENDS A 
RIDGE SE ACROSS THE FORECAST WATERS TO NEAR 18N115W. RECENT 
SCATTEROMETER DATA VERIFIED THE EXISTENCE OF FRESH TO STRONG 
TRADE WINDS BETWEEN THE SRN PERIPHERY OF THE RIDGE AND THE 
ITCZ...COVERING THE AREA FROM 09N TO 17N W OF 124W. DUE TO A 
TIGHT PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES OVER NW 
MEXICO...WINDS ARE ALSO EXPECTED TO INCREASE OVER THE NE PART OF 
THE FORECAST REGION N OF ABOUT 25N AND E OF 122W TO THE COAST OF 
BAJA CALIFORNIA DURING THE NEXT 12-24 HOURS. EXPECT NW WINDS OF 
20-25 KT AND BUILDING SEAS TO 10-11 FT IN THAT AREA. THESE 
MARINE CONDITIONS WILL PERSIST THROUGH 48 HOURS. 

LONG PERIOD CROSS EQUATORIAL SW SWELLS AT 14-16 SECONDS DOMINATE 
MOST OF THE FORECAST WATERS E OF 115W. THESE SWELLS ARE MERGING 
WITH NW SWELLS THAT COVER THE REMAINDER OF THE FORECAST WATERS. 
WAVEWATCH GUIDANCE SUGGESTS THAT THESE SWELLS WILL SLOWLY 
SUBSIDE ON TUE...EXCEPT FOR THE NE PORTION OF THE AREA WHERE A 
NEW SET OF NW SWELLS IS FORECAST TO IMPACT THAT REGION.  
 
$$ 
CHRISTENSEN